MAYBE
0.08/0.17	MAYBE
0.08/0.18	
0.08/0.18	Problem:
0.08/0.18	 f(x,empty()) -> x
0.08/0.18	 f(empty(),cons(a,k)) -> f(cons(a,k),k)
0.08/0.18	 f(cons(a,k),y) -> f(y,k)
0.08/0.18	
0.08/0.18	Proof:
0.08/0.18	 Open
0.08/0.18	EOF